It is not entirely clear why obesity seems to promote cancer, but one potential factor is inflammation.
Studies show that fat cells spew into the bloodstream a variety of inflammatory proteins known as cytokines , which have been found to stimulate cancer cells. Many scientists believe this chronic state of inflammation caused by fat cells is also one of the reasons people with obesity have higher rates of complications from Covid-19.
https://www.nytimes.com/2022/06/03/well/weigh...dit-eng30s